hi..i have a problem with my 93 mercedes 300se the interior heat is not working will someone please tell me how to check the monovalve to see if its working thanks for you help and time.

What do you mean heat not working? No fan speed or just no heat?

Do you hear the flap moving to put heat to floor or dash?

Aux heat pump in hood siezed maybe?

If you disconnect the monovalve you should get full heat (will revert to open position when disconnected by design). Although I think 140 chassis all had duovalve, (left/right heat control)
Gilly

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